Process for achieving a wear resistant translucent surface on surface elements

ABSTRACT

A process for achieving a wear resistant translucent surface on surface elements ( 1 ) which comprises a decorative upper layer ( 2 ) and a supporting core ( 5 ). A number of layers of UV- or electron-beam curing lacquer are applied on a decorative surface, through a process comprising the steps; 
     i) Applying a base layer of lacquer to a surface weight of 5-50 g/m 2 . 
     ii) Applying hard particles with an average particle size in the range 10-150 μm which are sprinkled to an amount of 1-40 g/m 2  on the still wet lacquer. 
     iii) Curing the applied layer of lacquer to a desired viscosity. 
     iv) Applying a covering layer of lacquer to a surface weight of 5-150 g/m 2 . 
     v) Curing the applied layer of lacquer to a desired viscosity. 
     vi) Applying a topcoat layer of lacquer with an additive of 5-35% of hard particles with an average size in the range 50 nm-30 μm to a surface weight of 2-20 g/m 2 . 
     vii) Curing the applied layers of lacquer to a desired final viscosity.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a process for achieving a wear resistant translucent surface on surface elements with a decorative upper surface of which the decorative elements have an considerably improved matching of the décor between adjacent surface elements.

2. Description of the Related Art

Products clad with thermosetting laminate is common in many areas nowadays. They are mostly used where the demands on abrasion resistance are high, and furthermore where resistance to different chemicals and moisture is desired. As examples of such products floors, floor skirtings, table tops, work tops and wall panels can be mentioned.

The thermosetting laminate most often consist of a number of base sheets with a decor sheet placed closest to the surface. The decor sheet can be provided with a pattern by desire. Common patterns usually visualise different kinds of wood or mineral such as marble and granite.

One common pattern on floor elements is the rod pattern where two or more rows of rods of, for example wood, is simulated in the decor.

The traditional thermosetting laminate manufacturing includes a number of steps which will result in a random matching tolerance of up to ±5 mm, which is considered to great. The steps included in the manufacturing of a laminate floor is; printing decor on a paper of α-cellulose, impregnating the decorative paper with melamine-formaldehyde resin, drying the decorative paper, laminating the decorative paper under heat and pressure together with similarly treated supporting papers, applying the decorative laminate on a carrier and finally sawing and milling the carrier to the desired format. All these steps in the manufacturing will cause a change in format on the decor paper. It will therefore be practically impossible to achieve a desired match of patterns between the elements of a without causing great amounts of wasted laminate. The thermosetting laminate is a rather costly part of a laminate floor.

SUMMARY OF THE INVENTION

It has, through the present invention, been made possible to overcome the above mentioned problems and a surface element with a decorative surface where the decorative pattern between different surface elements is matching has been obtained. The invention relates to a process for achieving décor on surface elements which comprises a decorative upper layer and a supporting core.

The surface elements may be used as floor, wall or ceiling boards. The surface elements are suitably manufactured through the following process;

i) A supporting core with a desired format is manufactured and provided with an upper side and a lower side.

ii) The upper side of the supporting core is then provided with a decor, by for example printing. The décor is positioned after a predetermined fixing point on the supporting core.

iii) The upper side of the supporting core is then provided with a protecting, at least partly translucent, wear layer by for example spray coating, roller coating, curtain coating and immersion coating or by being provided with one or more sheets of α-cellulose impregnated with thermosetting resin or lacquer.

The décor is preferably achieved by digitisation of an actual archetype or by partly or completely being created in a digital media. The digitised décor is preferably stored digitally in order to be used as a control function and original, together with control programs and selection parameters, when printing the décor.

The dimensions of the surface to be covered by surface elements is suitably entered into the terminal and support programs calculates an installation pattern. The installation pattern calculation is suitably also used for printing an assembly instruction. In order to visualise the selection the installation pattern calculation is possibly used for printing a miniaturised copy of the calculated installation with the selected pattern and décor. The dimensions of the surface to be covered by surface elements is suitably entered into the terminal and that that support programs further calculates décor and segmentation pattern matching between the surface elements.

The selections is preferably also used, together with support programs for controlling further steps in the manufacturing procedure selected from the group; identification marking, positioning marking, packaging, lacquering, surface embossing, storing and delivery logistics.

An algorithm is suitably used for guiding the positioning of the décor segments and segmentation pattern so that a décor segment from one surface element may continue on an adjoining surface element. The control program is suitably used, together with décor data and selection parameters, for applying matching identification on the surface elements.

Thus, the invention relates to a process for achieving a wear resistant translucent surface on surface elements which comprises a decorative upper layer and a supporting core. The invention is characterised in that a number of layers of UV- or electron-beam curing lacquer are applied on a decorative surface, through a process comprising the steps;

i) A base layer of lacquer is applied to a surface weight of 5-50 g/m².

ii) Hard particles with an average particle size in the range 10-150 μm are then sprinkled to an amount of 1-40 g/m² on the still wet lacquer.

iii) The applied layer of lacquer is then cured to a desired viscosity.

iv) A covering layer of lacquer is then applied to a surface weight of 5-150 g/m².

v) The applied layer of lacquer is then cured to a desired viscosity whereupon,

vi) a topcoat layer of lacquer with an additive of 5-35% of hard particles with an average size in the range 50 nm-30 μm is applied to a surface weight of 2-20 g/2.

The applied layers of lacquer are cured to a desired final viscosity.

The lacquer is suitably a UV or electron beam curing acrylic, epoxy or maleimide lacquer. The lacquer does suitably comprise a reaction mechanism selected from the group; cationic, free-radical, and thiol-ene, and is preferably photo initiator free.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a surface element formed in accordance with the process of the invention.

FIG. 2 shows a first process scheme in accordance with the invention.

FIG. 3 shows a second process scheme in accordance with the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to an embodiment of the invention second base layer of lacquer is applied to a surface weight of 5-50 g/m² on top of the sprinkled hard particles after the curing process. A second layer of hard particles with an average particle size in the range 10-150 μm is then sprinkled to an amount of 1-40 g/m² on the still wet lacquer of the second base layer whereupon the applied layer of lacquer is cured to a desired viscosity before applying the covering layer.

The base layer is suitably applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m². The covering layer is suitably applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m². The topcoat layer is also suitably applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m².

The décor is suitably achieved by digitisation of an actual archetype or by partly or completely being created in a digital media. The digitised décor is stored digitally in order to be used as a control function and original, together with possible control programs, when printing the décor.

The décor may accordingly be obtained by making a high resolution or selected resolution digital picture of the desired décor. This is suitably made by means of a digital camera or scanner. The most common décor will of course be different kinds of wood and minerals like marble, as these probably will continue to be preferred surface decoration in home and public environments. It is, however, possible to depict anything that is visible. The digitised version of the décor is then edited to fit the size of the supporting core. It is also possible to rearrange the décor in many different ways, like changing colour tones, contrast, dividing the décor into smaller segments and adding other decorative elements. It is also possible to completely create the décor in a computer equipped for graphic design. It is possible to create a simulated décor so realistic that even a professional will have great problems in visually separating it from genuine material. This makes it possible to make for example floor boards with an almost perfect illusion of a rare kind of wood, like ebony or rose wood and still preserving trees under threat of extermination.

The digital décor is used together with guiding programs to control a printer. The printer may be of an electrostatic type or an ink-jet type printer. The resolution needed is much depending on the décor that is to be simulated, but resolutions of 10-1500 dots per inch (dpi) is the practical range in which most decors will be printed. Under normal conditions a resolution of 300-800 dpi is sufficient when creating simulations of even very complex decorative patterns and still achieve a result that visually is very difficult to separate form the archetype without close and thorough inspection.

The digitally stored décor can also be used together with support programs when guiding other operations and procedures in the manufacturing process. Such steps in the operation may include procedures like identification marking, packaging, lacquering, surface embossing, storing and delivery logistics as well as assembly instructions.

It is advantageous to manufacture the supporting core in the desired end user format and to provide it with edges suited for joining before applying the décor and wear layer, since the amount of waste thereby is radically reduced. The décor matching tolerances will also be improved further by this procedure.

The main part of the supporting core is suitably constituted by a particle board or a fibre board. It is, however, possible to manufacture the core that at least partly consist of a polymer such as for example polyurethane or a polyolefin such as polyethylene, polypropylene or polybutene. A polymer based core can be achieved by being injection moulded or press moulded and can be given its shape by plastic moulding and does therefore not require any abrasive treatment. A polymer based core may except polymer also contain a filler in the form of a particle or fibre of organic or inorganic material, which besides the use a cost reducing material also will be used to modify the mechanical characteristics of the core. As an example of such suitable fillers can be mentioned; cellulose or wood particles, straw, starch, glass, lime, talcum, stone powder and sand. The mechanical characteristics that may be changed is for example viscosity, thermal coefficient of expansion, elasticity, density, fire resistance, moisture absorption capacity, acoustic properties, thermal conductivity, flexural and shearing strength as well as softening temperature.

The upper surface, i.e. the surface that is to be provided with décor, is suitably surface treated before the printing. Such surface treatment will then incorporate at least one of the steps, ground coating and sanding. It is also possible to provide the surface with a structure that matches the décor that is to be applied.

The translucent wear layer is suitably constituted by a UV- or electron beam curing lacquer such as an acrylic, epoxy, or maleimide lacquer. The wear layer is suitably applied in several steps with intermediate curing where the last one is a complete curing while the earlier ones are only partial. It will hereby be possible to achieve thick and plane layers. The wear layer suitably includes hard particles with an average particle size in the range 50 nm-150 μm. Larger particles, in the range 10 μm-150 μm, preferably in the range 30 μm-150 μm, is foremost used to achieve abrasion resistance while the smaller particles, in the range 50 nm-30 μm, preferably 50 nm-10 μm is used for achieving scratch resistance. The smaller particles is hereby used closest to the surface while the larger ones are distributed in the wear layer. The hard particles are suitably constituted of silicon carbide, silicon oxide, α-aluminium oxide and the like. The abrasion resistance is hereby increased substantially. Particles in the range 30 mm-150 mm can for example be sprinkled on still wet lacquer so that they at least partly become embedded in finished wear layer. It is therefore suitable to apply the wear layer in several steps with intermediate sprinkling stations where particles are added to the surface. The wear layer can hereafter be cured. It is also possible to mix smaller particles, normally particle sizes under 30 μm with a standard lacquer. Larger particles may be added if a gelling agent or the like is present. A lacquer with smaller particles is suitably used as top layer coatings, closer to the upper surface. The scratch resistance can be improved by sprinkling very small particles in the range 50 nm-1000 nm on the uppermost layer of lacquer. Also these, so called nano-particles, can be mixed with lacquer, which with is applied in a thin layer with a high particle content. These nano-particles may besides silicon carbide, silicon oxide and α-aluminium oxide also be constituted of diamond.

The décor on the surface elements is suitably constituted by a number of decor segments with intermediate borders, which borders, on at least two opposite edges coincides with intended, adjacent surface elements.

It is also desirable to provide the surface elements with a surface structure intended to increase the realism of the décor of the surface elements. This is suitably achieved by positioning at least one surface structured matrix, forming at least one surface structure segment on a corresponding décor segment or number of décor segments on the decorated surface of the surface element in connection to the application of wear layer. This matrix is pressed towards the wear layer whereby this will receive a surface with structure that enhances the realism of the décor.

When simulating more complex patterns, like wood block chevron pattern or other decors with two or more divergent and oriented decors, it is suitable to use at least two structured matrixes which forms one structure segment each. The structure segment are here independent from each other in a structure point of view. The surface structure segments are intended to at least partly but preferably completely match the corresponding décor segments of the décor. The surface structure segments are accurately positioned on the décor side of the surface element in connection to the application of the wear layer, and is pressed onto this whereby the wear layer is provided with a surface structure where the orientation of the structure corresponds to the different directions in the décor.

One or more matrixes preferably forms the surface of one or more rollers. The surface element is then passed between the roller or rollers and counter stay rollers, with the décor side facing the structured rollers. The structured rollers are continuously or discontinuously pressed towards the décor surface of the surface element.

Rollers containing two or more matrixes, is suitably provided with a circumference adapted to the repetition frequency of change of direction in the décor.

It is also possible to apply the structure matrixes on the surface of a press belt. The surface element is then passed between the press belt and a press belt counter stay under continuous or discontinuous pressure between the structured press belt and the press belt counter stay.

It is, according to one alternative procedure, possible to have one or more matrixes form the structure surface of one or more static moulds which momentary is pressed towards the decorative side of the surface element.

According to one embodiment of the invention, particularly characteristic decor segments such as borderlines between simulated slabs, bars, blocks or the like and also knots, cracks, flaws and grain which is visually simulated in the décor, is stored as digital data. Said data is used for guiding automated engraving or pressing tools when providing said characteristic décor segments with a suitable surface structure, and that said engraving tool or pressing tool is synchronised via the predetermined fixing point on the surface element.

According to an alternative embodiment of the invention a random structure is achieved by utilising at least one roller provided with an elastic and structured surface. A wear layer is achieved as described above after which the surface structure is applied. A roller covered with a structured elastic layer is pressed towards the upper surface of the surface element while it passes. A doctor roller transfers a selected amount of UV-curing lacquer to the structured roller which then transfers lacquer to the upper surface of the surface element. The depth and appearance of the structure achieved can be guided through the following parameters;

The depth, selected structure and elasticity of the structured roller.

The force used for pressing the doctor roller towards the structured roller.

The amount of lacquer transferred by the doctor roller.

The force used for pressing the structured roller towards the surface element.

If a thin layer of lacquer is applied on the doctor roller, the pressure between doctor roller and structured roller is low to moderate only the raised and protruding parts of the surface of the structured roller will be covered with lacquer. If also the pressure between the structured roller and the surface element is low to moderate, lacquer will be transferred to the surface element in a pattern corresponding to the protruding pattern of the structured roller. If the pressure between the structured roller and the surface element is high parts of the lacquer will be urged from the surfaces in contact resulting in ridges on both sides of the same contacting surfaces. If the amount of lacquer on the doctor roller is increased, these ridges will be thicker and wider to a point where a negative impression of the structure is achieved. It is also possible to achieve a similar effect by increasing the force between the doctor roller and the structured roller.

Since a roller is used for achieving the structure a certain repetition of the structure can be noted when distinct pattern occurs even though some variation can be achieved by varying the parameters above. The repetition frequency can be altered by changing the diameter of the roller. It is also possible to utilise a belt with structure. Such a belt can be made very long whereby the structure will repeat itself very seldom.

It is also possible to utilise two or more structured rollers with different diameter, otherwise utilising the process as described above. This will make it possible to achieve an endless variation in structure pattern, especially since all rollers used can be set individually at different pressure and layer thickness. A surface structure with a clearly notable pattern and without any notable repetition in the structure will create a more living surface and will give the impression of being hand-crafted.

The lacquer used for the structuring of the surface preferably contains 5-20% by weight of hard particles of for example α-aluminium oxide, silicon oxide or silicon carbide with an average particle size in the range 2-15 μm. This will, above adding to the wear resistance of the wear layer as a whole, also prolong the time before the structure part of the surface is worn down. The lacquer is cured with a predetermined amount of UV-light after the application stage whereby it cures to the desired strength. It is also possible to utilise a heated glazing roller after the curing stage. This will make it possible to make the edges between the structure layer and the adjacent surface sharper and more well defined. This will make the structure more distinct. It is also possible to simulate very small, micro structure features as, for example, pores that normally occur in wood by pressing hard structured rollers on the cured structured surface achieved above.

The process described in the present application, for manufacturing surface elements is very advantageous from a logistic point of view since the number of steps when achieving a new décor is radically reduced. It is, according to the present invention possible to use digitally created or stored data for directly printing the décor on a surface element by using a ink-jet printer or a photo-static printer. The so-called set up time will thereby be very short, whereby even very special customer requirements may be met at a reasonable cost. It is according to the present invention possible to manufacture, for example, a world map in very large format, stretching over a great number of surface elements without any disrupting deviations in décor matching, to mainly the same cost as bulk produced surface elements. Since the décor may be handled digitally all the way to the point of being applied to the surface of the core, set up times will be practically non-existent while at the same time a high degree of automation will be practicable. It is also possible to automatically provide the surface elements with identification and orientation marking which would make the installation of complex decors, like world maps in the example above, much easier. This has so far been impossible.

Surface elements manufactured as described above is suitably used as a floor covering material where the demands on stability and scratch and abrasion resistance is great. It is, according to the present invention, also possible to use the surface elements as wall and ceiling decorative material. It will however not be necessary to apply thick wear layer coatings in the latter cases as direct abrasion seldom occurs on such surfaces.

The invention is described further in connection to an enclosed figure, embodiment examples and schematic process descriptions showing different embodiments of the invention.

Accordingly, FIG. 1 shows parts of surface element 1 which includes an upper decorative layer 2, edges 3 intended for joining, a lower side 4 and a supporting core 5. The process is initiated by manufacturing a supporting core 5 with a desired format and edges 3 intended for joining. The supporting core 5 is further provided with an upper side 1′ suited for printing and a lower side 4. The upper side 1′ of the supporting core 5 is then provided with a décor 2′ by printing, or by utilizing an ink-jet printer. The décor 2 is oriented after a predetermined fixing point on the supporting core 5. The upper side 1′ of the supporting core 5 is then provided with a protecting translucent wear layer 2″ through curtain coating. The supporting core 5 is constituted by particle board or fibre board. The translucent wear layer 2″ is constituted by a UV-curing acrylic lacquer which is applied in several steps with intermediate curing, of which the last one is a complete curing while the earlier ones are only partial curing. The wear layer 2″ also includes hard particles of α-aluminium oxide with an average particle size in the range 0.5 μm to 150 μm.

A surface structured matrix is positioned and pressed towards the décor side of the surface element 1 before the final curing of the acrylic lacquer whereby the surface of the wear layer 2″ receives a surface structure 2′″ which enhances the realism of the décor 2′.

It is also possible to utilise two or more surface structured matrixes, each forming a structure segment, between which the structure is independent, which will make it possible to simulate the surface structure of, for example, wood block chevron pattern décor.

A supporting polymer and filler based core is manufactured in the desired format and is provided with an upper side, a lower side and edges provided with joining members, such as tongue and groove. The upper side of the supporting core is then sanded smooth after which a primer is applied. A décor is then applied on the upper side by means of a digital photo-static five colour printer. The colours are magenta, yellow, cyan, white and black. The décor is positioned from a predetermined fixing point in form of a corner of the supporting core, while the décor direction is aligned with the long side edge initiating from the same corner.

The basis for the décor is stored as digital data. This digital data has been achieved by digitising a number of wood grain patterns with a digital camera. A number of rectangular blocks with a fixed width, but of varying length is selected and parted from the digital wood grain pictures. The width of the rectangular blocks is selected so that three block widths equals the width of a supporting core. The digital image of the wood blocks are then classified after wood grain pattern and colour so that a number of groups is achieved. The groups are; fair wood with even grain, dark wood with even grain, fair wood with knots and flaws, dark wood with knots and flaws, fair cross-grained wood and finally dark cross-grained wood. Each group contains five different block simulations. An algorithm is feed into a computer which is used for the guiding of the printing operation so that the simulated wood blocks is digitally placed in three longitudinal rows and mixed so that two similar wood blocks never is placed next to each other. The algorithm will also guide the position of the latitudinal borderlines between the simulated wood blocks so that they are unaligned with more than one block width between adjacent rows. It will also guide the latitudinal position of the borderlines so that it either aligns with the shorter edges of the supporting core or is unaligned with more than one block width. Another printer, also guided by the computer, is utilised for printing a running matching number on the lower side short side edges. The décor will hereby continue longitudinally over the surface elements and a perfect matching is obtained when the surface elements are placed in numerical order.

A basic layer of UV-curing acrylic lacquer is then applied by means of a rollers. Particles with an average particle size in the range 150 μm is then sprinkled onto the still wet basic layer, whereby the main layer of UV-curing acrylic lacquer is applied by spray coating. The two layers of lacquer are then partly cured using UV-light whereby the viscosity of the lacquer increases. A top layer of UV-curing acrylic lacquer with an additive in the form of hard particles with an average size of 2 μm, is then applied by means of a roller. Hard particles with an average size of 100 nm is then sprinkled on top of the wet top layer, whereby the lacquer is partly cured with UV-light so that the viscosity increases. The still soft lacquer is then provided with a structure in the form of narrow, small, elongated recesses, simulating the pores of the wood. This will increase the realism of the décor. This is achieved by alternating between two different structured roller per row of simulated wood blocks. The structure of the rollers simulates even wood grain and cross-grained wood respectively. The rollers are alternately pressed towards the lacquered surface while it passes. The positioning of the rollers are guided via the digitally stored data used for printing the décor as well as the fixing point used there.

It is according to one alternative embodiment possible to utilise one or more static moulds with surface structure which momentary is pressed towards the décor side.

Especially characteristic décor segments such as borderlines between slabs, bars, blocks or the like and also knots, cracks, flaws and grain which is visually simulated in the décor, is suitably stored as digital data. This data is achieved by processing selected parts of the simulated wood blocks so that guiding data is achieved. Said data is then used for guiding an automated robot provided with an engraving tool or a press mould which provides the surface of the lacquer with a structure that matches said characteristic décor segments. The operation is also here synchronised via the predetermined fixing point on the supporting core.

The lacquer is then completely cured with UV-light to desired strength, whereby the finished surface elements may be inspected by the naked eye or by a digital camera supported by a computer. The surface elements are then packed in batches and provided with identification markings.

The process above will make it possible to have a completely customer driven manufacturing where even very small quantities may be produced with the same efficiency as bulk manufacturing. Even though only one décor is described in. connection to the process scheme above, it becomes clear to anyone skilled in the art, that a décor is changed very easily in the process. All of the important steps of the manufacturing such as printing, structuring, inspection, packaging and identification marking may be controlled and supervised by central processing data. This will make it logistically possible to manufacture customer designed décors. Such a process is exemplified as follows;

The customer utilises a database via Internet or at a local dealer. It is also possible for another operator utilise the database. The database contains samples and/or reduced resolution copies of a great variety of standard décors which can be combined after predetermined parameters.

The parameters may, for example, concern a single surface element where, for example, chevron pattern, diamond pattern and block pattern may be the choices of décor segmentation. It will here be possible to select a set of different simulations to randomly or by selected parameters fill the segments, for example, marble, birch and mahogany. The customer may also add an inlay from a design of his own which is digitised and processed, preferably automatically, to a desired format and resolution.

The parameters may alternatively include décor segments that requires the space of several surface elements, for example a map over the world. The parameters may here further include fading of the larger design to a surrounding décor, surrounding frame of other décor etc.

The customers enters the measurements of the surface that is to be covered by the surface elements. The customer then makes selections from the database and is able to see his selection as a completed surface, either on screen or by printing. The visualisation program used, is suitably also used for calculating installation pattern and presenting installation instructions with identification numbers on surface elements and where to cut the elements in order to make a perfect match. The surface elements may also be provided with removable matching lines on the decorative side making matching of décor between adjacent rows easier. The customer or dealer may then confirm his order via electronic mail where the pattern and décor is reduced to a code sequence and the order can be the direct input to the computer guiding the manufacturing process as described above. The customer and/or dealer data follows the manufacturing process all the way to packaging and a fully customer guided manufacturing process is achieved.

A supporting fibre board based core is manufactured in the desired format and is provided with an upper side, a lower side and edges. The upper side of the supporting core is then sanded smooth after which a white primer is applied. A décor is then applied on the upper side by means of a digital ink-jet four colour printer. The colours are magenta, yellow, cyan and black. The décor is positioned from a predetermined fixing point in form of a corner of the supporting core, while the décor direction is aligned with the long side edge initiating from the same corner.

The basis for the décor is stored as digital data. This digital data has been achieved by digitising a number of wood grain patterns with a digital camera. A number of rectangular blocks with a fixed width, but of varying length are selected and parted from the digital wood grain pictures. The width of the rectangular blocks is selected so that three block widths equals the width of a finished surface element. The digital image of the wood blocks are then joined digitally to form a rectangular surface of a specified size, for example, 200×1200 mm. A selected amount of such combinations of different blocks are designed as described above so that a number of slightly different rectangular surfaces is achieved. The printer, or preferably a set of printers are positioned so that a desired number of rectangular décor surfaces with a specified intermediate distance is printed on the supporting core. The intermediate distance between the rectangular surfaces is the distance needed for parting and moulding of edges. The décor printer or printers are also used for printing fixing points at predetermined positions. Another printer, also guided by the computer, is utilised for printing an identity code on the lower side of each intended finished surface element.

A basic layer of UV-curing acrylic lacquer is then applied by means of rollers. Particles with an average particle size in the range 150 μm is then sprinkled onto the still wet basic layer, whereby a top layer of UV-curing acrylic lacquer with an additive in the form of hard particles with an average size of 2 μm, is applied by means of a roller. Hard particles with an average size of 100 nm is then sprinkled on top of the wet top layer, whereby the lacquer is partly cured with UV-light so that the viscosity increases. The still soft lacquer is then provided with a structure in the form of narrow, small, elongated recesses, simulating the pores of the wood. This will increase the realism of the décor. This is achieved by pressing rollers towards the lacquered surface while it passes. The positioning of the rollers are guided via the digitally stored data used for printing the décor, as well as the fixing point used there when more complex and completely matching surface structures as described together with process scheme 1 is desired.

The lacquer is then completely cured with UV-light to desired strength, whereby the finished surface element is cut into the predetermined formats which are provided with edges with joining functionality are moulded by milling. The cutting and edge moulding process is positioned from fixing point printed close to the décor. The surface elements may then be inspected by the naked eye or by a digital camera supported by a computer. The surface elements are then packed in batches and provided with identification markings.

It is, according to an alternative procedure in the process, possible to cut and mould the edges at an earlier stage in the process. It is suitable to apply and cure a protecting layer of lacquer on top of the printed décor followed by cutting and moulding of the edges. The remaining and main part of the wear layer is then applied as described in connection to process scheme 1 or 2 above.

The process above will make it possible to have a customer initiated manufacturing where even very small quantities may be produced with the same efficiency as bulk manufacturing. Even though only one décor is described in connection to the process scheme above, it becomes clear anyone skilled in the art, that décors is changed very easily in the process. All of the important steps of the manufacturing such as printing, structuring, inspection, packaging and identification marking may be controlled and supervised by central processing data.

The Invention is Also Described Through Embodiment Examples EXAMPLE 1

A supporting core of medium density fibre board were sanded smooth. A layer of primer lacquer were applied on top of the fibre board. The primer were cured after which a décor was printed on top of the primer.

The build up of a wear layer was then initiated by applying 30 g/m² of UV-curing acrylic lacquer by means of roller coating. 20 g/m² of hard particles made of α-aluminium oxide with an average particle size of 70 μm were sprinkled on the still sticky lacquer. The lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. Another 30 g/m ² of UV-curing acrylic lacquer was then roller coated onto the already applied layer after which another 20 g/m² of α-aluminium oxide particles with an average particle size of 70 μm were sprinkled on the still sticky second coating. The lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. Three layers of UV-curing acrylic lacquer was then applied by roller coating with intermediate partial curing as a above. Each of the three layers had a surface weight of 20 g/m². The hard particles were completely embedded in the lacquer after the three layers were applied and a plane upper wear layer surface was achieved.

A top coating procedure was then initiated. A first layer of UV-curing acrylic topcoat lacquer was applied by means of a roller coater on top of the previous, partly cured, layers. The topcoat lacquer contained 10% by weight of hard particles of α-aluminium oxide with an average particle size of 10 μm. The first layer was applied to a surface weight of 10 g/m². The topcoat lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. A second layer of the topcoat lacquer was then applied and partly cured as described above. The wear layer was then provided with a surface structure by means of a surface structured roller. A third layer of the topcoat formulation was then applied on top of the structured wear layer. Also the third layer of top coat was applied to a surface weight of 10 g/m². The wear layer was then exposed to a predetermined energy amount of UV-light so that it cured completely.

The wear layer was then tested for abrasion resistance according to ISO 4586/2-88, where an IP value of 7100 turns was obtained. An IP value of 7100 turns is fully sufficient for floor covering materials with medium to heavy traffic like hotel lobbies, hallways and the like.

EXAMPLE 2

A supporting core of medium density fibre board were sanded smooth. A layer of primer lacquer were applied on top of the fibre board. The primer were cured after which a décor was printed on top of the primer. The build up of a wear layer was then initiated by applying 30 g/m² of UV-curing acrylic lacquer by means of roller coating. 20 g/m² of hard particles made of α-aluminium oxide with an average particle size of 70 μm were sprinkled on the still sticky lacquer. The lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. Another 30 g/m² of UV-curing acrylic lacquer was then roller coated onto the already applied layer after which another 20 g/m² of α-aluminium oxide particles with an average particle size of 70 μm were sprinkled on the still sticky second coating. The lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. Three layers of UV-curing acrylic lacquer was then applied by roller coating with intermediate curing as a above. Each of the three layers had a surface weight of 20 g/m². The hard particles were completely embedded in the lacquer after the three layers were applied and a plane upper wear layer surface was achieved. Also the uppermost of the three layers of lacquer was cured to a desired viscosity.

A second décor layer was then printed on top of the wear layer. The second decor layer, which was identical to the first décor closest to the core, was oriented and positioned so that it completely matched the first décor.

The build up of an upper wear layer was then initiated by applying 30 g/m² of UV-curing acrylic lacquer by means of roller coating. 20 g/m² of hard particles made of α-aluminium oxide with an average particle size of 70 μm were sprinkled on the still sticky lacquer. The lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. Another 30 g/m² of UV-curing acrylic lacquer was then roller coated onto the already applied layer after which another 20 g/m² of α-aluminium oxide particles with an average particle size of 70 μm were sprinkled on the still sticky second coating. The lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. Three layers of UV-curing acrylic lacquer was then applied by roller coating with intermediate curing as a above. Each of the three layers had a surface weight of 20 g/m². The hard particles were completely embedded in the lacquer after the three layers were applied and a plane upper wear layer surface was achieved.

A top coating procedure was then initiated. A first layer of UV-curing acrylic topcoat lacquer was applied by means of a roller coater on top of the previous, partly cured, layers. The topcoat lacquer contained 10% by weight of hard particles of α-aluminium oxide with an average particle size of 10 μm. The first layer was applied to a surface weight of 10 g/m². The topcoat lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. A second layer of the topcoat lacquer was then applied and partly cured as described above. The wear layer was then provided with a surface structure by means of a surface structured roller. A third layer of the topcoat formulation was then applied on top of the structured wear layer. Also the third layer of top coat was applied to a surface weight of 10 g/m². The wear layer was then exposed to a predetermined energy amount of UV-light so that it cured completely.

The wear layer was then tested for abrasion resistance according to ISO 4586/2-88, where an IP value of 13500 turns was obtained. An IP value of 13500 turns is fully sufficient for floor covering materials with heavier traffic like airports, railway stations and the like. The second layer of décor and wear layer will add abrasion resistance without having obtained an unwanted hazy effect in the décor.

EXAMPLE 3

A supporting core of medium density fibre board were sanded smooth. A layer of primer lacquer were applied on top of the fibre board. The primer were cured after which a decor was printed on top of the primer.

The build up of a wear layer was then initiated by applying 15 g/m² of UV-curing acrylic lacquer by means of roller coating. 20 g/m² of hard particles made of α-aluminium oxide with an average particle size of 70μm were sprinkled on the still sticky lacquer. The lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. One layer of UV-curing acrylic lacquer was then applied by roller coating and was partially cured as above. The layer had a surface weight of 40 g/m². The hard particles were embedded in the lacquer after the layer of lacquer was applied and a mainly plane upper wear layer surface was achieved.

A top coating procedure was then initiated. A first layer of UV-curing acrylic topcoat lacquer was applied by means of a roller coater on top of the previous, partly cured, layers. The topcoat lacquer contained 10% by weight of hard particles of α-aluminium oxide with an average particle size of 10 μm. The first layer was applied to a surface weight of 10 g/m². The topcoat lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. The wear layer was then provided with a surface structure by means of a surface structured roller. A second, final layer of the topcoat formulation was then applied on top of the structured wear layer. Also the second layer of top coat was applied to a surface weight of 10 g/m². The wear layer was then exposed to a predetermined energy amount of UV-light so that it cured completely.

The wear layer was then tested for abrasion resistance according to ISO 4586/2-88, where an IP value of 3100 turns was obtained. An IP value of 3100 turns is fully sufficient for floor covering materials with light traffic like bedrooms, living rooms and the like.

EXAMPLE 4

A supporting core of medium density fibre board were sanded smooth. A layer of primer lacquer were applied on top of the fibre board. The primer were cured after which a decor was printed on top of the primer.

The build up of a wear layer was then initiated by applying 50 g/m² of UV-curing acrylic lacquer which contained 10% by weight of hard particles of α-aluminium oxide with an average particle size of 10 μm by means of roller coating. The lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased.

A top coating procedure was then initiated. A first layer of UV-curing acrylic topcoat lacquer was applied by means of a roller coater on top of the previous, partly cured, layer. The topcoat lacquer contained 10% by weight of hard particles of α-aluminium oxide with an average particle size of 10 μm. The first layer was applied to a surface weight of 10 g/m². The topcoat lacquer was then exposed to a predetermined energy amount of UV-light so that it cured only partly and the viscosity was increased. The wear layer was then provided with a surface structure by means of a surface structured roller. A second, final layer of the topcoat formulation was then applied on top of the structured wear layer. Also the second layer of top coat was applied to a surface weight of 10 g/m². The wear layer was then exposed to a predetermined energy amount of UV-light so that it cured completely.

The wear layer was then tested for abrasion resistance according to ISO 4586/2-88, where an IP value of 300 turns was obtained. An IP value of 300 turns could be sufficient for floor covering materials with light traffic like bedrooms, living rooms and the like.

The invention is not limited to the embodiments shown as these can be varied in different ways within the scope of the invention. It is for example possible to achieve a random structure is by utilising at least one roller provided with an elastic and structured surface which is pressed towards the upper surface of the surface element while it passes. A doctor roller transfers a selected amount of UV-curing lacquer to the structured roller which then transfers lacquer to the upper surface of the surface element. The lacquer is then cured with a predetermined amount of UV-light after the application stage whereby it cures to the desired strength. 

What is claimed is:
 1. A process for achieving a wear resistant translucent surface on surface elements which comprises a decorative layer and a supporting core, wherein a number of layers of UV- or electron-beam curing lacquer are applied on a surface element, through a process comprising the steps; i) applying a base layer of lacquer to a surface weight of 5-50 g/m² whereupon, ii) first hard particles being at least one selected from the group consisting of silicon carbide, silicon oxide, α-aluminum oxide and diamond, with an average particle size in the range 10-150 μm are sprinkled to an amount of 1-40 g/m² on the still wet lacquer whereupon, iii) the applied layer of lacquer is cured to a desired viscosity whereupon; iv) a covering layer of lacquer is applied to a surface weight of 5-150 g/m² whereupon, v) the applied layer of lacquer is cured to a desired viscosity whereupon, vi) a topcoat layer of lacquer with an additive of 5-35% by weight of second hard particles being at least one selected from the group consisting of silicon carbide, silicon oxide, α-aluminum oxide and diamond with an average particle size in the range 50 nm-30 μm is applied to a surface weight of 2-20 g/m² whereupon, vii) the applied layer of lacquer is cured to a desired viscosity whereupon, viii) a matrix provided with a surface, is pressed towards the applied layers of lacquer, structure, the surface structure comprising at least one raised section, the surface structured matrix being selected from the group consisting of a press plate, a press belt, a roller, several rollers or a combination thereof, thereby providing the wear resistant translucent surface with a surface structure whereupon, ix) the applied layers of lacquer are cured to a desired final viscosity.
 2. A process according to claim 1, wherein at least one lacquer is a UV or electron beam curing acrylic, epoxy or maleimide lacquer.
 3. A process according to claim 1, wherein at least one lacquer comprises a reaction mechanism selected from the group consisting of cationic, free-radical, and thiol-ene, and is photo initiator free.
 4. A process according to claim 1, wherein the base layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m².
 5. A process according to claim 1, wherein the covering layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m².
 6. A process according to claim 1, wherein the topcoat layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 2-20 g/m².
 7. A process according to claim 2, wherein the base layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m².
 8. A process according to claim 3, wherein the base layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m².
 9. A process according to claim 2, wherein the covering layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m².
 10. A process according to claim 3, wherein the covering layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 5-40 g/m².
 11. A process according to claim 2, wherein the topcoat layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 2-20 g/m².
 12. A process according to claim 3, wherein the topcoat layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 2-20 g/m².
 13. A process according to claim 4, wherein the topcoat layer is applied in several steps with intermediate curing to a desired viscosity, each step comprising application of lacquer to a surface weight of 2-20 g/m². 